This application claims priority on International Application No. PCT/GB01/02317, filed May 25, 2001, which claims priority on British Application No. 0129340.4, filed May 26, 2000.
This invention relates to a peristaltic pump mechanism.
Peristaltic pumps are widely used in many industries, but particularly in the medical industry for pumping of body fluids or fluids to be received by a patient, since there is no need to provide any valves, which could possibly leak, nor is there any contamination of the liquid to be pumped since the liquid is not contacted by component parts of the pump, lubricants used in the pump and so on. In a peristaltic pump, the liquid to be pumped passes through a flexible tube which is compressed by at least one roller, arranged to run along the length of the tube. The roller serves to close the tube and so isolate at the point of compression liquid downstream the tube from liquid upstream the tube. Then, on moving the roller along the tube, the liquid downstream the tube is driven further downstream, and so is pumped by the roller.
A typical peristaltic pump has a static flexible tube arranged in a part-circular form around the periphery of a pump wheel which carries a plurality of arcuately-spaced rollers and each of which engages and compresses the tube. To ensure a sufficient compression of the tube, a sleeve usually surrounds the outer periphery of the tube so that the compression takes place between the roller and the inner surface of the sleeve. Then, on rotation of the pump wheel, liquid will be pumped around the tube in the direction of rotation of the wheel, and by having a plurality of rollers so that at least two rollers are at all times engaged with, and compress, the tube, back-leakage is prevented.
With the configuration of peristaltic pump described above, there is no slippage between the rollers on the wheel and the tube. Thus, the pump may be expected to have a long working life with only minimal wear of the tube, as the rollers run around the tube. The tube may thus form part of some other equipment and is located within the sleeve for pumping as the wheel rotates, whenever a liquid associated with the equipment is to be pumped. However, location of the tube between the pump sleeve and the rollers can be difficult to achieve and there is the likelihood of the tube being damaged.
The alternative is to provide the flexible tube as a part of the pump, in which case connections must be made to each end of the flexible tube, whenever a liquid is to be pumped, and this leads to the possibility of foreign matter entering the tube when the pump is disconnected from the equipment. Further, contamination may occur on making the connections, or following a previous use of the pump, for pumping a different liquid.
A principal aim of the present invention is to provide a peristaltic pump mechanism which allows the connection of the mechanism to a flexible tube through which a liquid is to be pumped in a particularly simple manner, without compromising the efficacy of the pump and the advantages of a peristaltic pump.
According to the present invention, there is provided a peristaltic pump mechanism comprising a base plate having a generally planar surface on which is defined a circular path, the planar surface being adapted for supporting sheets of flexible plastic between which is defined a part-circular pump tube whereby the pump tube will extend partially around said circular path when said sheets are supported on said surface, an operating section, a hinge connecting the operating section to the base plate so as to be movable between an open position where the sheets of plastic may be positioned on the planar surface of the base plate with said pump tube aligned with the circular path and a pumping position where the operating section overlies said planar surface, a releasable catch mechanism adapted to hold the operating section in said pumping position, three like rotatable pumping elements arranged with their axes substantially at 120xc2x0 to each other and mounted on the operating section locally to compress said pump tube and to roll around the circular path of the base plate when the operating section is in its pumping position, each said pumping element being of conical shape and mounted on the operating section so that the axis of the element is substantially co-incident with the center of the circular path in the plane of the planar surface whereby essentially no slippage takes place between the conical surface of each pumping element and the flexible sheets supported on the planar surface of the base plate, and power drive means to cause the pumping elements to roll around the circular path.
It will be appreciated that with the present invention, the flexible pump tube is constrained to lie on a generally planar surface and the pump elements roll around the tube, on that planar surface. Friction, and so wear of the tube, is avoided by providing pump elements of an appropriate conical form and mounted such that essentially no slippage takes place between the tube and the pump elements.
There are three pumping elements arranged with their respective axes angularly equi-spaced around the circular path and all driven for simultaneous movement around that path. In this way, back leakage through the pump may be avoided, since the tube will be closed off by compression at all times, by at least one of the pump elements.
Further to ensure that no slippage occurs between the pump elements and the pump tube, each pump element is preferably provided with gearing arranged to cause the pump element to rotate without slippage with respect to the base plate.
So as to facilitate separation of the operating section and the base plate, and to facilitate connection together of those components, it is preferred that the operating section is pivoted to the base plate, a catch arrangement being provided to hold the operating section in its xe2x80x9cclosedxe2x80x9d position parallel to the base plate. Means may be provided to permit pre-setting of the gap between the upper surface of the base plate and the plane of the lower surfaces of the pumping elements, so as to allow proper accommodation of the pump tube. In the alternative, one of the components may be spring-loaded, whereby the spring force allows accommodation of the pump tube, for compression by each pumping element.
The pump tube preferably is configured to facilitate its incorporation within the pump mechanism. Advantageously, the pump tube is formed integrally with a sheet of flexible plastics material and the base plate and operating section have co-operating means to locate the sheet in a pre-defined position on the base plate. For example, such means may comprise at least one pin mounted on either the base plate or the operating section, so as to project the other component, and then be received in a recess in the other component when the two components are joined together. The sheet of flexible material may then have an appropriately positioned aperture for each pin, whereby the sheet is positively located with respect to the base sheet.
This invention extends to a peristaltic pump of this invention as described above in combination with a peristaltic tube component arranged to deliver liquid in a controlled manner to some other site, which component comprises a pair of overlying flexible sheets bonded together to define a tube-like passageway therebetween and which extends from one common edge of the sheets to another common edge of the sheets, a portion of the passageway intermediate the ends thereof being of part-circular shape for compression by a pump member rolling around a circular path coincident with said portion of the passageway of part-circular shape when the component is mounted on a peristaltic pump, the ends of the passageway being configured to permit the connection thereto of ducts for the transfer of liquid to and from the passageway, and the sheets being profiled and adapted to permit the connection thereto of a peristaltic pump device co-operable with the tube-like passageway to control the flow of liquid through the passageway.